Hi guys,
i need some advice on using the various airwaves in air(including Wifi waves) to generate some electricity. and if it is possible to charge mobile.
I heard somewhere that it is possible to charge mobile by infrared. I am not sure how it works. we have a mini project in our third year of engineering. I need advice for the same.
If any 1 of u have some detail regarding this , pls post here.
thankyou

The radio waves that surround us don't have enough energy to be used to charge batteries or power anything and wi-fi is very low power. Microwaves can be used to transmit power but the power levels involved would be fairly lethal for anyone that gets in the way.

Seems I read an article on Edn.com in their Design Ideas section several months back that some fellow wrote - he was using the sounds from the street to charge a supercapacitor by using a piezo element and rectifying the output voltage.

would u please direct me to the link.
Actually i am more intrested in displaying the wireless charging. I may even use a 500w bulb to provide the required light to the photosensor. or i may even use electromagnetic fields from a source to receiver to do the same.

The real problem is power densities, there just isn't much out there. Makes sense if you think about it, it would be waste product.

I have heard stories about people tapping into the EMF from high tension lines, but the stories always end up with them being busted by the power company, and possibly going to jail.

Think natural resources, solar, wind, geothermal, tides and/or waves. Unless it is truly a waste product, such as sound, you are likely going to tick off the person who created and owns the resource you're using for energy. There isn't free lunch, if you use radio waves to generate power then someone else (who has a legitimate use) won't be able to use them for their intended function.

I was thinking more of a 100ft antenna within a mile of a commercial AM radio station, say a class one. There the legalities get a little complicated. I suspect at the least they can sue in civil court, but recievers aren't as rigidly controlled by FCC rules as transmitters. At most you would get is a watt or two though, power densities again.

Back in my learning days I regularly feed 50 to 100ft of wire (the whole spool) between trees for my crystal radio. There I was using the radio waves to power my earphone. Same thing, but completely legal, and the station I was listening to would approve.